Fix query and logic for retrieving a particular locale stats for acs-lang admin/index page. In particular, messages that do not exist in a certain locale are properly computed in order to calculate deleted and untranslated ones, at the price of executing one query per locale instead of just a big one.

Refactor acs-lang 'admin/index' page, adding the new columns 'total' and 'deleted' to the listing, and reworking the query so it is faster (53ms -> 7ms), correct (number of messages by state are computed coherently with other acs-lang pages) and gives more information

Add deleted column to acs-lang 'package-list', and fixed number of messages depending on status, making it coherent with 'message-list'. Also fixed translated/untranslated count on default locale in 'message-list'. Version bump.

Add 'message-undelete' page to make use of the new '::message::undelete' proc for undeleting messages, a couple of icons, the undelete option in 'message-list' and the undelete action in automated tests